Given an n-length Array of integers ranging from -1000 to 1000 find the largest product of three numbers in A that you can get.
[-3,2,6,4,8] => 192
There are three basic scenarios that can produce the largest product:
- The largest three positive numbers
- The largest positive number and the smallest two negative numbers
- The largest three negative numbers
The first task is to sort the array, that means that the largest numbers are at the right and the smallest area on the left.
Something like this, with a, b and c being the smallest values and x, y, and z being the largest values.
The first scenario happens when
x*y is greater than
a*b. Consequently, the second scenario only occurs when
a*b is greater than
x*y. We will always use z in these two scenarios because it is the largest positive number and two negatives will always give a positive.
The third scenario only occurs when z is less than 0. In this case, we now want the smallest absolute value which happens to be the largest number.
[-4, -5, 1, 2, 7, 9, 10]
x * y = 7 * 9 = 63which is greater than
a * b = -5 * -4 = 20
[-9, -8, -7, 1, 2, 3]
x * y = 2which is less than
a * b = 72
[-5, -4, -3, -2, -1] z is negative,
This leads to the following code
- You shouldn’t do operations on A because that mutates the A outside the function. So here normally we’d have created a copy
const aCopy = [...A];
negativeProductcould be named better.
And that’s that.